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Lightening the pull on a slip joint.

M

mdsmith

Joined
Jan 7, 2009
Messages
1,495
Hey guys. I have one of the GEC Schrade fire and ice trappers. It's a great knife with a perfect fit and finish, but the pull is too stiff for my liking. I'm wondering, if I took my Dremel, and rounded off the corners of the part of the blade that contacts the back spring, would this make the pull a little easier?
 
It is the thickness of the spring that primarily accounts for how much force is needed to open a blade. Friction between blade tang and liners can add to the amount of force needed to open a blade.
With a blade partly open so that it's spring is displaced, this area can be flushed out under running warm water and using a small amount of dish soap and a tooth brush. Then flush with just water and dry it out with a hair dryer. Then spray a number of times with WD-40 and finally lubricate it with a few drops of mineral oil. This should ensure that any grit that might have been present in the joint has been flushed out and good lubrication is now present. Then open and close the blade 100+ times. Most likely it will then be a bit easier to open.
I have not heard of anyone trimming the tang corners and i don't see how this would make a difference. Surface area for friction would not be substantially reduced and the spring still needs to be flexed to open the blade.
The real fix is to take the knife apart and shave down the spring but that's not something most of us can do.
roland
 
Thanks for the response. It's not so much the pull while the blade is in motion. It's more the effort required to get the blade moving. I hope that makes sense. I figured that when you first pull on the blade to open it, you are initially feeling the sharp corner of the tang against the spring, then you hit the half stop. I thought the having a slightly rounded tang, may ease this.

It also seems that by removing some material from the corner of the tang, you would be reducing the amount that the back spring needs to flex.
 
Take a look at this post by sitflyer. I have had good results following his "time out box" spring stretching exercise in lightening a hard pull.

Edited to say, I used it on the pen blade of the Case 6207 I got from you, and it lightened up nicely.
 
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Yes, I did round the corners, and it did help in my case...I used a jewlers file with some strips of 400 grit wet dry sandpaper wrapped around it, it was a bit time consuming as I wanted the job to look neat...word of caution...tape the edge of the blade as you will be working in close proximity to it, as the edge you want to break will be exposed with the knife in the open position...
 
I took one stiff knife and worked the action without adding oil. With the pivot dry and clean, it seemed the metal smoothed out pretty quickly. The tang/spring junction seemed to spit some tiny metal filings. I am sure. Though I thing they actually came off either the spring or the tang shoulders.

You can also leave the blade partially open for a while.

I have never tried filing the tang corners my self, though I have sanded a kick or two to get a blade flush.

You can't put it back! So take it slow and easy!
 
Hey Matt,

That particular knife has had a mineral oil treatment but has not had Roland's suggested protocol applied. Really hope you find an answer that works.
 
Thanks Bemo. I love the knife, I just want to keep all of my fingers. :)

I tried cleaning out the joints, which didn't really seem gritty to start with(which makes sense after your post), and applied some 3 in 1 oil.
 
Been there and done all of the above fixes. To make a long story short I finally had to return the knife to GEC.
So now I start waiting. Mine is a #73 Beaver Tail.
Hopefully a return to GEC will make it a knife I feel comfortable using. Makes me appreciate my Case knives.
 
You've got to be careful with removing material from that area. The tang is gauged so that the spring sits flush in the open and closed position, if you remove material from the area of the tang that rests on the spring, you'll alter that balance. You may also wind up raising the point of the blade above the liners, although this can easily be fixed by filing some of the kick down. If you have to take a lot off the kick, you wind up dropping the spring betwen the liners in the closed position. The easiest way to lighten spring tension is to take some of the spring down at and a bit forward of the center pin. This would require a decent belt sander or grinder, or a trip to GEC.

Eric
 
Would removing the sharp corner on the tang effect resting spring height? I would think rounding that corner would just make a smoother camming action. Just thinking outloud, which is probably more dangerous than trying to open that knife.
 
Eric, so using a belt sander you would also be taking down the liners and covers. Right ? I just want to be sure i understand this procedure.
roland
 
bemo said:
Would removing the sharp corner on the tang effect resting spring height? I would think rounding that corner would just make a smoother camming action. Just thinking outloud, which is probably more dangerous than trying to open that knife.
Click to expand...
On my Barlow, the sharp tang corners were dragging on the spring, Galling, and the resulting drag caused an incredibly hard pull...rounding the tang eased this considerably, and in no way affects spring height open or closed.
 
Most of my user GECs get a tang rounding. They can rip up pockets in a nasty way otherwise. No spring problems etc.

Would like to soften the spring on my Primitive Bone 26, but since it's a single spring 2 blades I'm nervous of giving it the open&close workout. I never open both blades at the same time on a single-spring knife either.
 
Will, in this case i think the corner to be rounded is next to the blade edge, not the pocket ripper corner of the blade spine.
If i'm wrong about which tang corner might help with the pull, will someone please correct me.
thanks, roland
 
Bemo, As long as you're not taking too much off it shouldn't affect it, take a little down at a time and keep checking it. A small four sided tapered fine diamond file works nicely for a job like that. Polish it up a bit with some fine grit paper when you're done to keep it smooth, and watch out for burrs.


Roland, yes you'd take everything down. I should have said that it's easy if you've got a lot of tools, you'd need several different grit belts and a buffer too, but it works well!:o:D

Eric
 
I rounded the corners of the tang on my GEC 73 Beaver Tail. Did help a little but still had some serious problems opening. I sent it back to GEC. That little bit of corner rounding on the tang voided the warranty. So we will see what if any thing they do about it. Best to send it back if it isn't right to start with.
 
Well, it ended up breaking in nicely with just some oil and a lot of opening and closing. It's really perfect now. Nice firm, but totally manageable pull.
 
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